A sister and brother make contact with the biological father they’ve never met in The Kids Are All Right, a charming movie about marriage and family.

College-bound Joni (Mia Wasikowska) and her 15-year-old brother Laser (Josh Hutcherson) were raised in an upwardly mobile suburban southern California family by moms Nic (Annette Bening) and Jules (Julianne Moore). Biologically, their link to each other is through their “father” — the sperm donor that each mom used when she conceived a kid (Nic had Joni, Jules had Laser — though both kids call both women mom and the intra-family alliances aren’t always genetically determined). When Joni turns 18, Laser, who watches longingly as a friend wrestles with his dad, pushes her to contact the sperm bank and find out who the donor is. Soon, Joni finds herself on the phone with Paul (Mark Ruffalo), a modern-hippie chef with an organic garden for his restaurant and a slew of younger female employees giving him the googley-eyes. He’s stunned when she calls but once he meets Joni and Laser he wants to see more of them. He seems besotted with the idea of having teenage children in the same way you could see him besotted by a connection who can get him free-range chicken.

Though Laser had pushed Joni to find him, it’s Joni who seems to be quickly enamored of having a dad, whereas Laser doesn’t always seem to know what to make of Paul. It’s this confusion that leads his moms to ask him what’s troubling him and leads him to spill the story of Paul. Nic and Jules are scared and hurt and unsure how to proceed — so they invite him over for dinner. A more laid back woman herself, Jules sort of takes to Paul, agreeing to design his back yard as a kick-start to her landscaping business. For Nic, Paul seems like nothing but a threat and she pours herself endless glasses of wine to get through the meal. It is, of course, only the beginning of the upset Paul brings to the order of family life.

I try not to read reviews of movies before I write my reviews, but it’s been impossible to avoid the extremely high praise given to this movie. I tried not to go in with inflated expectations but I did and I can see why the movie has won so much acclaim. Marriage almost never gets any serious study in mainstream-ish movies. Usually, married characters have to be trying to kill each other, having outrageous extramarital sex or near death before a movie puts them at the dramatic center. One of the things that made Knocked Up such a stand-out film was that, in its own Judd Apatow way, it looked at the idea that marriage can be difficult and yet still something you don’t want to give up on. Near the end of The Kids Are All Right, Julianne Moore makes a speech that basically says just that — marriage is really, really tough and frustrating and occasionally lonely but the whole point of a marriage, of family, is that you can’t give up just because it gets difficult. What makes Nic and Jules parents to Joni and Laser, and Paul just a genetically similar acquaintance, is the same kind of I-am-here-no-matter-what struggle that turns people who are dating into a married couple.

The fact that this couple is made up of two women is so secondary to the point that you could almost write a review without mentioning it. It is the gimmick that makes Paul’s presence possible and so particularly intrusive — his maleness is the one thing this high-achieving couple can’t give their children. The movie pokes fun at the yuppie-ness of its couple but it also underlines, just in case it isn’t already apparent, that it’s the marriageness of a marriage (and not the ability of those two specific people to mix their genes to create a baby) — the sticking it out and pulling together and devotion of one person to another and other such vague but critical things — that makes it such an important relationship in our individual lives as well as for society in general. Nic and Jules are married people — adrift at times, hurt at times, confused by the other person, but married in an unshakeable way.

And it’s hard, as a movie critic, not to get all gooey about this much actual life portrayed on screen. You just don’t see that kind of thing every day at the multiplex.

Add to that the general greatness of everyone involved. Annette Bening does tightly wound with aplomb and here lets it get nice and tense before she unravels at, say, the sight of her daughter on a motorcycle or the unearned admiration her kids have for Paul. Moore is equally entertaining — she’s a good parent but you can see how insecurity nips at her. So often we get characters who are either a mess or too perfect, and Moore’s Jules is a smart mix of the two. Meanwhile, Mark Ruffalo is the very picture of flakey awesomeness. He’s the kind of guy you can’t help but like but who would drive you nuts if you had to count on him. (You Can Count On Me was his breakout role and he reminds you here of all that made him so fascinating in that movie.) And the kids —Wasikowska and Hutcherson — are perfect. They are delightfully age-appropriate in their speech and outlook. Hutcherson in particular has really aged thoughtfully from his very genuine kid performances in movies like Zathura and Bridge to Terabithia.

The Kids Are All Right is the rare summer movie that deserves its outsized praise. A

Rated R for strong sexual content, nudity, language and some teen drug and alcohol use. Directed by Lisa Cholodenko and written by Cholodenko and Stuart Blumberg, The Kids Are All Right is an hour and 46 minutes long and is distributed in limited release by Focus Features.